Chat failing with “Confirm”

The Messenger icon shows on the right side, and you can type into the box – but when you send the message – it comes back with “Confirm” – if you click that, it goes to a PageNotFound page on facebook?

What’s happening here?

I have Manychat and ChatFuel running on the Messenger for Facebook thing. But eveything else works

The page I need help with: [log in to see the link]